An SDN is a new type of innovative network architecture, and a core technology OpenFlow thereof separates a control plane of a network device from a data plane, so as to implement flexible control over network traffic and provide a good platform for innovation of a core network and applications.
In an SDN network, each network device only retains a forwarding function, and all control functions are centralized in a controller. The SDN network includes a host, a forwarding device, and a controller. The host is a network endpoint, and is an initiator a terminator of communication; the forwarding device is responsible for sending a data packet, and has no independent control plane and shares a centralized control plane (that is, the controller in the SDN) with other devices; and the controller is a control center in the SDN, and is responsible for controlling and managing the forwarding device. When communication is performed between hosts, a communications channel is obtained by computation of the controller instead of negotiation of the forwarding device, and is delivered to each forwarding device.
The controller in the SDN implements control and management using software modules such as a software logic, a north bound interface, a Network Operating System (NOS), and a south bound interface. The control logic is a network application program or service, and interacts with the NOS using the North Bound Interface (NBI), so that the NOS controls the forwarding device through the South Bound Interface (SBI), thereby implementing functions, such as data forwarding, required by the control logic.
In the prior art, if a link is required to be established between two hosts that are registered in different controllers, it is necessary to use two switching devices, which are separately registered in different control devices, to perform an operation. When one controller needs to perform an operation for a host under the other control device, the operation is implemented using a broadcast mechanism such as subscription/notification, and all switching devices under the other control device may receive an event request and perform determining, resulting in low performance of service processing.